Orthoterminal Correction of Congenit a1 Cardiovascular Defects
T
he distinction between a palliative and a corrective operation has become blurred recently. A resurgence of interest in techniques of bypassing the right ventricle has culminated in successful right atrium-to-pulmonary artery shunts for the treatment of tricuspid atresia, as first reported by Fontan and Baudet [l]. These procedures result in neither normal anatomy nor normal physiology. Can they properly be called corrective? If so, in what sense are they corrective? Are they curative? If not, then are they merely palliative? The terms palliation, correction, and cure should be reexamined in the light of recent technical advances. A new term, orthoterminal correction, may be useful in clarifying the concepts underlying corrective operations.
REPAIR OF FUNCTION
The function of the cardiovascular system is to perfuse the pulmonary and systemic capillary beds with adequate amounts of physiologically appropriate blood. The blood perfusing one of the two capillary beds is physiologically appropriate only if it last traversed the other bed, that is, pulmonary preceding systemic or systemic preceding pulmonary capillary exposure. Functional heart disease is present when the system of pumps, conduits, and valves is unable to achieve sequential perfusion with volumes adequate to meet metabolic needs. T o be corrective, a heart operation must produce a cardiovascular system able to maintain two separate circulations in series with one another, perfusing the systemic capillary beds with adequate amounts of oxygenated blood and perfusing the lungs with adequate amounts of unsaturated blood. PALLIATION
Palliate derives from the Latin pallium, meaning “cloak.” T o palliate is to cloak the disease, to mitigate the pathophysiology while leaving the basic abnormality uncorrected. For example, a systemic-to-pulmonaryartery shunt for a patient with tetralogy of Fallot is palliative: it improves systemic arterial oxygenation and relieves symptoms due to desaturation, but it leaves the intracardiac lesion untouched and the capillary beds perfused with large quantities of inappropriate blood. CORRECTION
Correction of cardiac abnorpalities can be achieved at several levels. The highest is anatomical correction; for example, repair of atrial or ventricular septa1 defect. After this type of procedure the only deviation from normal is the presence of $car tissue or a small piece of prosthetic material.
The next level is physiological correction; for example, repair of tetralogy of Fallot. Operation cannot alter the abnormal relationship of the aortic root to the left ventricle, but direction of flow through the proper cardiac chambers and normal pressure relationships can be restored. A type of repair that produces a cardiovascular system still further from normal is hemodynamic correction; for example, the Mustard procedure for transposition of the great arteries. Normal cardiovascular pressures and flows can be restored by this procedure, but the reversal of the usual ventricular relationships results in nonphysiological stresses on the tricuspid valve and right ventricular muscle. Clearly, Fontan’s operation fits none of these categories of correction. Systemic venous return is directed from the superior vena cava and right atrium into the pulmonary arteries, and through the lungs, left atrium, ventricle, and aorta. Hemodynamic correction is not achieved since the absence of an anatomical ventricle in the right heart circuit results in abnormally high systemic venous pressures and a narrow pulmonary artery pulse pressure. Yet there may be no signs of right heart failure in a patient who is pink and has normal exercise tolerance. Cardiovascular function, by the definition provided above, has been restored. In order to describe this fourth variety of correction and to distinguish it from the other three, the word orthoterminal (derived from the Greek orthos, “correct,” and termon, “end”) is suggested. Of the four types, orthoterminal correction produces a cardiovascular system the furthest from the range of normal. CURE
Cure of a specific heart disease is permanent correction of the functional abnormality. Although the phrase curative operation in the strictest sense can be used only after a significant number of patients have lived a normal lifespan after correction, the evidence to date is that functional repair after operation for such anomalies as atrial and ventricular septal defect persists for as long as follow-up has been possible. Therefore, corrective operations for those lesions may justifiably be called curative; at least they are, to borrow an idea from oncology, twenty-year cures. No palliative operation can be curative. Some corrective operations are curative, but many are not. For example, replacement of an abnormal valve with a prosthetic valve during childhood is a corrective operation, but limitations of annulus size and durability of currently available prostheses will eventually necessitate replacement of those valves; therefore such operations cannot be considered curative. Indeed, until more nearly ideal valve substitutes are found, all cardiac valve replacements must be considered corrective but not curative. In describing a particular operation, residual pathophysiology can be noted when appropriate: for example, repair of a high-pressure ventricular septal defect shoiild be described as anatomical correction of ventricular
106
THE ANNALS OF THORACIC SURGERY
Editorial septa1 defect with residual pulmonary vascular obstructive disease. Such a repair may be curative if the pulmonary vascular disease regresses and a normal lifespan ensues, or it may be fatal if advanced vascular disease is present. Over the next few years the operation introduced by Fontan and Baudet or similar orthoterminal procedures will be used with increasing frequency to treat not only tricuspid atresia but other previously uncorrectable lesions as well. These might include some forms of single ventricle and hypoplastic left heart syndrome. Abnormal hemodynamics after such operations should not lead to the conclusion that the procedures are only palliative. They are, in a meaningful sense, corrective. Whether or not they are curative will be discovered by long-term follow-up. The term orthoterminal correction should help to clarify the concept of functional repair of cardiac lesions.
ROBERTM. SADE, M.D. T h e Children’s Hospital Medical Center 300 Longwood Ave. Boston, Mass. 02115
Reference I . Fontan, F., and Baudet, E. 26240, 1971.
Surgical repair of tricuspid atresia. Thorax
VOL.
19, NO.
1, JANUARY,
1975
107
T
he distinction between a palliative and a corrective operation has become blurred recently. A resurgence of interest in techniques of bypassing the right ventricle has culminated in successful right atrium-to-pulmonary artery shunts for the treatment of tricuspid atresia, as first reported by Fontan and Baudet [l]. These procedures result in neither normal anatomy nor normal physiology. Can they properly be called corrective? If so, in what sense are they corrective? Are they curative? If not, then are they merely palliative? The terms palliation, correction, and cure should be reexamined in the light of recent technical advances. A new term, orthoterminal correction, may be useful in clarifying the concepts underlying corrective operations.
REPAIR OF FUNCTION
The function of the cardiovascular system is to perfuse the pulmonary and systemic capillary beds with adequate amounts of physiologically appropriate blood. The blood perfusing one of the two capillary beds is physiologically appropriate only if it last traversed the other bed, that is, pulmonary preceding systemic or systemic preceding pulmonary capillary exposure. Functional heart disease is present when the system of pumps, conduits, and valves is unable to achieve sequential perfusion with volumes adequate to meet metabolic needs. T o be corrective, a heart operation must produce a cardiovascular system able to maintain two separate circulations in series with one another, perfusing the systemic capillary beds with adequate amounts of oxygenated blood and perfusing the lungs with adequate amounts of unsaturated blood. PALLIATION
Palliate derives from the Latin pallium, meaning “cloak.” T o palliate is to cloak the disease, to mitigate the pathophysiology while leaving the basic abnormality uncorrected. For example, a systemic-to-pulmonaryartery shunt for a patient with tetralogy of Fallot is palliative: it improves systemic arterial oxygenation and relieves symptoms due to desaturation, but it leaves the intracardiac lesion untouched and the capillary beds perfused with large quantities of inappropriate blood. CORRECTION
Correction of cardiac abnorpalities can be achieved at several levels. The highest is anatomical correction; for example, repair of atrial or ventricular septa1 defect. After this type of procedure the only deviation from normal is the presence of $car tissue or a small piece of prosthetic material.
The next level is physiological correction; for example, repair of tetralogy of Fallot. Operation cannot alter the abnormal relationship of the aortic root to the left ventricle, but direction of flow through the proper cardiac chambers and normal pressure relationships can be restored. A type of repair that produces a cardiovascular system still further from normal is hemodynamic correction; for example, the Mustard procedure for transposition of the great arteries. Normal cardiovascular pressures and flows can be restored by this procedure, but the reversal of the usual ventricular relationships results in nonphysiological stresses on the tricuspid valve and right ventricular muscle. Clearly, Fontan’s operation fits none of these categories of correction. Systemic venous return is directed from the superior vena cava and right atrium into the pulmonary arteries, and through the lungs, left atrium, ventricle, and aorta. Hemodynamic correction is not achieved since the absence of an anatomical ventricle in the right heart circuit results in abnormally high systemic venous pressures and a narrow pulmonary artery pulse pressure. Yet there may be no signs of right heart failure in a patient who is pink and has normal exercise tolerance. Cardiovascular function, by the definition provided above, has been restored. In order to describe this fourth variety of correction and to distinguish it from the other three, the word orthoterminal (derived from the Greek orthos, “correct,” and termon, “end”) is suggested. Of the four types, orthoterminal correction produces a cardiovascular system the furthest from the range of normal. CURE
Cure of a specific heart disease is permanent correction of the functional abnormality. Although the phrase curative operation in the strictest sense can be used only after a significant number of patients have lived a normal lifespan after correction, the evidence to date is that functional repair after operation for such anomalies as atrial and ventricular septal defect persists for as long as follow-up has been possible. Therefore, corrective operations for those lesions may justifiably be called curative; at least they are, to borrow an idea from oncology, twenty-year cures. No palliative operation can be curative. Some corrective operations are curative, but many are not. For example, replacement of an abnormal valve with a prosthetic valve during childhood is a corrective operation, but limitations of annulus size and durability of currently available prostheses will eventually necessitate replacement of those valves; therefore such operations cannot be considered curative. Indeed, until more nearly ideal valve substitutes are found, all cardiac valve replacements must be considered corrective but not curative. In describing a particular operation, residual pathophysiology can be noted when appropriate: for example, repair of a high-pressure ventricular septal defect shoiild be described as anatomical correction of ventricular
106
THE ANNALS OF THORACIC SURGERY
Editorial septa1 defect with residual pulmonary vascular obstructive disease. Such a repair may be curative if the pulmonary vascular disease regresses and a normal lifespan ensues, or it may be fatal if advanced vascular disease is present. Over the next few years the operation introduced by Fontan and Baudet or similar orthoterminal procedures will be used with increasing frequency to treat not only tricuspid atresia but other previously uncorrectable lesions as well. These might include some forms of single ventricle and hypoplastic left heart syndrome. Abnormal hemodynamics after such operations should not lead to the conclusion that the procedures are only palliative. They are, in a meaningful sense, corrective. Whether or not they are curative will be discovered by long-term follow-up. The term orthoterminal correction should help to clarify the concept of functional repair of cardiac lesions.
ROBERTM. SADE, M.D. T h e Children’s Hospital Medical Center 300 Longwood Ave. Boston, Mass. 02115
Reference I . Fontan, F., and Baudet, E. 26240, 1971.
Surgical repair of tricuspid atresia. Thorax
VOL.
19, NO.
1, JANUARY,
1975
107
